For resource saving, energy saving, and environmental protection, the society increasingly demands reduction in carbon dioxide gas emission. In order to also reduce the carbon dioxide gas emission of cars, various measures have been considered, including car weight reduction and the use of electric energy.
A common challenge in the automotive field is the need to enhance fuel efficiency by improving rolling resistance of tires, and there are also increasing demands for enhanced safety during driving and enhanced durability. Since these properties greatly depend on the performance of tires, tires for cars are increasingly required to have improved fuel efficiency, wet grip performance, handling stability, and durability (e.g. abrasion resistance). The performance of tires depends on various factors, including the structure and materials of tires, and greatly depends particularly on the performance of the rubber composition used in the tread part which comes into contact with the road surface. For this reason, a wide range of studies have been undertaken to technically improve rubber compositions for tires such as for treads and these techniques have been put into practical use.
For improving fuel efficiency and wet grip performance of rubber compositions, silica is widely used as a reinforcing filler but it has less reinforcing property compared to that of carbon black and there is a problem that durability such as abrasion resistance is deteriorated. In order to solve such problem, for example, JP2000-344955 A discloses a technique of using a modified butadiene as a rubber component in a rubber composition comprising silica and JP2013-177539 A discloses a technique of using a modified styrene-butadiene copolymer as a component constituting a rubber composition. However, a further improvement of the performance is required.